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'[EE] Ground reference resistor'
2011\07\20@130732 by V G

picon face
On this page http://www.colomar.com/Shavano/intro_opamp2.html the guy talks
about a ground reference resistor (10k), attached to the output of the
opamp.

Why is it needed? What is he talking about when he says "ground reference"?
Isn't the opamp signal relative to ground anyway

2011\07\20@132451 by Herbert Graf

picon face
On Wed, 2011-07-20 at 13:07 -0400, V G wrote:
> On this page http://www.colomar.com/Shavano/intro_opamp2.html the guy talks
> about a ground reference resistor (10k), attached to the output of the
> opamp.
>
> Why is it needed? What is he talking about when he says "ground reference"?
> Isn't the opamp signal relative to ground anyway?

The explanation in the text seems pretty clear to me:

"This is to provide a ground reference for the next active device that
this circuit is plugged into."

TTYL

2011\07\20@134410 by Sean Breheny

face picon face
To elaborate further, there is a DC-blocking capacitor in the signal
path. If you did not put the 10K to ground on the output side of the
DC-blocking cap, then there would be no way to draw any DC current
from the output. This would be a problem for some amplifiers which
need to draw a tiny input bias current (nanoamps or less). Without the
resistor, this would eventually charge up the capacitor to the full
rail voltage, or close to it, and then the circuit would clip and
distort the audio.

Sean


On Wed, Jul 20, 2011 at 1:26 PM, Herbert Graf <spam_OUThkgrafTakeThisOuTspamgmail.com> wrote:
{Quote hidden}

>

2011\07\20@140330 by V G

picon face
On Wed, Jul 20, 2011 at 1:44 PM, Sean Breheny <.....shb7KILLspamspam@spam@cornell.edu> wrote:

> To elaborate further, there is a DC-blocking capacitor in the signal
> path. If you did not put the 10K to ground on the output side of the
> DC-blocking cap, then there would be no way to draw any DC current
> from the output. This would be a problem for some amplifiers which
> need to draw a tiny input bias current (nanoamps or less). Without the
> resistor, this would eventually charge up the capacitor to the full
> rail voltage, or close to it, and then the circuit would clip and
> distort the audio.
>
>
Oh! I get it. Thanks. I totally missed the capacitor there. The function of
that block is a filter. Totally missed it.

Gonna do some simulations, keeping what you said in mind

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